You should have the extensions button. You can right-click that extension in the list or click the cog icon next to it and select Pin to Toolbar. If it isn't in the list, try the customize page. If it isn't there (and it probably isn't), press the button Restore defaults in the bottom right of that page. https://support.mozilla.org/en-US/kb/extensions-button https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars